The defending champion, who went head-to-head with Brazil's Thiago Braz late on Monday, compared his treatment to Jesse Owens at the 1936 Olympics before later apologising for the comment.

Boisterous, football-style support has been a feature of the Games but spokesman Mario Andrada agreed that the Brazilian fans went too far.

"As citizens of Brazil and as sports fans we don't think booing is the right attitude, even when you are in a one-to-one competition and a young Brazilian has the chance to beat the world champion," he said.

"We plan to intensify our dialogue with Brazilian fans through social networks to make sure that we behave as fans in a proper and elegant manner, without losing the passion for sport.